Extensor refers to muscle that extends a limb. Extensors are muscles that extend a limb, that is, increase the angle at a joint.
In psychology, the term "extensor" usually refers to a type of muscle that extends or straightens a limb or body part. Extensors are responsible for movements such as kicking, reaching, and straightening the back. The term "extensor" can also refer to a nerve that carries signals to these muscles.
Examples of extensor muscles include the quadriceps, which are responsible for extending the knee, and the triceps brachii, which are responsible for extending the elbow. Other examples include the extensor carpi radialis, which extends the wrist, and the erector spinae, which extend the back.
In some cases, issues with extensor muscles or nerves can lead to conditions such as muscle weakness, spasticity, or paralysis. Rehabilitation and physical therapy may be used to improve strength and range of motion in affected muscles.